Two calcium-binding proteins have been isolated from brain in this laboratory. Both proteins have a high degree of tissue specificity and may serve to underwrite specialized functions of calcium innervous tissue. We propose to continue the investigation of these two proteins in an effort to gain a greater understanding of their chemistry and physiological role. Toward that end, the proposed research will be directed along the following lines: 1. to improve the methods for isolating and purifying these proteins so that greater amounts may be made available for study; 2. to complete the chemical characterization and study of the calcium- binding properties of the less acidic of the two proteins, calcium-binding protein I (CBP I) in order to compare it with the second protein, CBP II, which has been studied extensively in this laboratory; 3. to prepare antisera to both proteins in order to facilitate immunochemical assay in brain and other tissues, and the study of their synthesis and phosphorylation, using immuneprecipitation; 4. to investigate the biochemical factors which regulate the levels and phosphorylation of the calcium-binding proteins in brain in an effort to establish a relationship between the presence of these proteins and neuronal function.